In silos of prior art types, particularly of the type utilizing a bottom unloader of the auger type that functions so as to move or sweep across the floor of a silo about a generally central axis, with the radial auger also being rotated on its own axis to engage compacted silage, loosen it and convey it toward the center of a silo, it has heretofore been known to utilize blades that cut silage and that have backwardly raked cutting edges, as for example, as is indicated in U.S. Pat. No. 3,391,809. In disclosures of the type of that patent and in other disclosures in the art, it is commonplace that the blades on a generally helical auger are arranged such that the cutting edges are backwardly raked with forward portions of the blade as viewed in the direction of rotation of the auger being shorter than rearward portions of that same blade. Each blade would, therefore, engage the silage in such a way as to cut it. Heretofore, it has generally been necessary to sharpen blades periodically as they became dull as caused by wear during operation from repeated engagement with and cutting of silage.